During the manufacture of electronic fuel injection throttle bodies, a precise interface is formed between the throttle plate and the main bore of the throttle housing. This interface is subject to variances imposed by small burrs and small dimensional tolerances. Prior to assembly into a vehicle, throttle body assemblies are set to a precise idle airflow to negate the effects of the plate/bore variance. As vehicles age, hydrocarbon deposits (sludge) form at the throttle plate/bore interface, causing a downward shift in the idle air flow. Current powertrain control systems (on-board computers) can correct for some shift in idle airflow, but excessive shift causes engine idle instability. To minimize the idle airflow shift, most manufacturers of throttle bodies pre-sludge (pre-condition) the throttle plate/bore interface, thereby minimizing the airflow effect of the naturally occurring hydrocarbon deposits (sludge). They do this by applying a sealant to the throttle plate or main bore during manufacture of the throttle body to simulate the effects of sludge build up.
The sealants currently in use for the pre-conditioning process use volatile organic solvents or water as their carrier mechanism. The sealer is applied and the solvent or water is then evaporated away to leave a durable sealant at the throttle plate/bore interface. In the case of sealants having volatile organic solvents, the evaporated solvent must be ventilated during application and curing, and precautions must be taken to prevent fire. In the case of water based sealants, the curing process can become very slow and is sensitive to temperature and humidity conditions, which must be accounted for to have a proper cure. The time for curing can be as much as eighteen minutes. This creates cost concerns associated with work in process inventory for the long cure time.
Thus, it is desirable to pre-sludge a throttle plate/bore interface with sealant having relatively fast cure times, substantially reduced ventilation requirements as compared to organic based solvents, and minimal concerns with changes in temperature and humidity on the curing process as compared to water based sealants.